Interactive tabletop is now receiving wide publicity for its natural setting for collaboration. However, few works have carefully studied the user interface management on tabletop, and many problems are still to be resolved. In this paper, we carry out a systematic research on tabletop UI management, and develop a system to facilitate user interaction on tabletop. Firstly, based on the analysis of tabletop’s horizontal display, multi-user usage and natural input features, we identify four fundamental requirements for tabletop UI management: input management, layout management, conflict management and authority management, which are significantly different from UI management on desktops. Secondly, we design a model for tabletop UI management. It contains a hierarchical structure for organizing surface elements, Object Manager for multi-user interface controlling, and Input Manager for processing concurrent multimodal inputs. Thirdly, we implement a system, uTablePlatform based on our model, and an SDK for users developing applications on uTablePlatform. At last, we carry out a user study, where four groups carry out a travel planning task using uTablePlatform. Results suggest that the UI management technique we present can help people complete individual or collaborative tasks effectively on tabletop.